Scientific Subsystems

Computer/Data Display

The Alvin data system provides real time data acquisition,
logging, display and general computing. A list of the data items
normally available for logging or display is provided in Appendix
A. Displayed data is viewed on the Alvin video system
as data overlays on video images.

The major “product” of the data system is the data
stored on the computer’s hard disk. After each dive this
data is transferred to the user in one of several different
ways. The normal media is 4.7GB DVD-Rs. File transfer from the
shipboard network via Ethernet is also available; guest computers
should be network-tested in advance and users should be prepared
to reconfigure network parameters in order to access the shipboard
net. Users must contact the Alvin Group prior to a cruise
if the estimate of data storage requirements (as described above)
exceeds 1MB per dive.

Digital Cameras

Digital cameras have been purchased for general use by scientists
using Alvin on R/V Atlantis. These cameras have
been gas-tested and are approved for use in the Alvin
sphere. Digital camera technology continues to improve, and
new features are being added to make these cameras more appropriate
for use in Alvin. As new products become available, they
will be made available to Alvin users. The characteristics
of onboard digital cameras are shown in the accompanying table.

Make/Model

Canon G2

Nikon D1

Canon G7

Zoom

34-102mm macro

52-105mm macro

34-102mm macro 3X

Focus

Auto/Manual

Auto/Manual

Auto/Manual

Resolution

2272x1704

2012x1324

2272x1704

File Format

JPEG/Canon RAW

TIFF/JPEG

JPEG/Canon RAW

Max size (MB)

2.0/2.9

7.8/1.3

2.9

Media Type

ATA I,II

ATA I,II

ATA I,II

Flash

Int/Ext

External

Int/Ext

These cameras allow the observers to take pictures through Alvin’s
viewports of seafloor features and animals or processes of interest
during the dive. They are most useful for documenting sampling
or instrument sites in order to aid post-dive debriefing and
planning for subsequent dives, as well as providing images suitable
for onboard web site preparation.

Investigators may also use their own cameras. If flash photography
is desired, the camera must be equipped with a hot shoe to accommodate
the remote trigger device. To prevent scratching of the viewports,
the lens ring on all cameras must be taped or otherwise isolated
by a soft material.

Several important points should be noted by potential users:

Do not put the lens up to the viewport. The viewports
are plastic and can be easily scratched; hold the lens so
that it is just off the viewport surface.

Familiarize yourself with the camera functions prior
to the dive -- groping around in the dark for the instructions
or trying to figure out the button settings on each camera
is not an efficient way to spend your dive time.

Pictures can be taken out the front or side viewports
using the HMI lights. The cameras can also be synched to
the external strobes via the infrared sending units connected
to cameras equipped with a hotshoe. For the digital cameras
there are several buttons that have to be pushed in order
to override the automatic settings; please consult the camera
manual onboard. Also check with the Alvin Expedition
Leader for details of flash use.

Shooting tips -- since lighting for the hand-held cameras
is provided by external strobes, shutter speed does not
control exposure. Bear in mind that shutter speed must be
within the strobe sync range, which is usually 1/125 second
or slower. 1/60 second works well. These settings are also
applicable to digital cameras while in the manual mode.

The above apertures are experimentally determined average
settings that are based on average color (reflectivity)
of subjects. If the subject is very dark then the aperture
should be opened one stop (e.g. 1-3 m = f2.8 with 400 ASA)
and if very bright (highly reflective) then the aperture
closed down one stop (1-3 m = f5.6). Be warned, however,
that the f-stop number may also be affected by particles
in the water and the flying height of the submersible.On
digital cameras the picture can be reviewed and the settings
adjusted as necessary for best exposure.

The viewports exhibit the least distortion when viewing
directly out the centerline. So for best photographs, keep
the camera pointed as directly out the viewport as possible
(perpendicular to the viewport surface). This is also the
area illuminated by the strobe and viewing lights.

It is advised that you set the focus distance at 7 ft. (2
meters) when the sub is moving since it is hard to focus
as the terrain moves by. When the sub is stationary you
can then focus on a particular subject. Telephoto lenses
have very little depth of field and are very difficult to
focus in the low light levels typical to this environment.

If time permits, external viewing lights should be turned
off after focusing. With the slow shutter speeds the external
lights will reduce the contrast of the picture.

Downloading images -- several options are available for
downloading the images either directly from the cameras
via cables onboard (see SSSG tech) or Flashcard media readers
(see SSSG tech and onboard crib sheets). You should be sure
to bring sufficient storage media (CD-ROMs or DVD-Rs) as
each of the highest quality images can be multi-MB in size.

Camera care -- please remember that these cameras are
for use by all scientists onboard and that investigators
joining the ship after your cruise are also planning on
using them. If there are problems with the cameras please
let the Alvin Expedition Leader or SSSG Tech know
immediately so they can be remedied. Please take good care
of them during your cruise so they can continue to provide
this capability for all science users.

Please consult with the Alvin Expedition Leader and SSSG
Tech when you get on board for more information and access to
the cameras.

Hand-held video camera
A hand-held digital camcorder (Sony DSR-PD100A as of June 2001)
is available for use by the observers for shooting through the
viewports. Its effective range extends approximately 2 meters
beyond the viewport. Lighting is supplied by external viewing
lights. Digital tape is not provided for this hand-held camcorder
and tapes made with this system will not be archived. Only Sony
DVM-60PR2 miniDV tapes are suitable for use in this camera.

Operation of the camera will be explained during orientation
or on request. It is suggested that observers practice with
the camera the evening before their dive to ensure familiarity
with the controls.

Basic basket Fibergrate platform

Basket load calculation diagram

Basket frame loaded with sampling devices

Science Basket

A generic 1.5" tubular pipe frame is fitted to the front of the submersible to accomodate science tools, equipment and collected samples. A fiberglass grate, 36" wide by 48" long serves as the base platform, to which an assortment of dive-specific equipment can be attached. Instruments are then either bolted through or haose clamped to the grate. Devices to be deployed or recovered as part of the dive evolution should be supplied with a holster or quiver that will secure the device (without the aid of one of the submerisble's manipulators) during sub launch and recovery.

The science basket assembly must be jettisonable in the event of entanglement, bottom fouling or if added buoyancy is needed for any reason. Accordingly, all equipment attached to the basket must have the ability to be released with the basket. Alvin Operations provides disconnect "boots" for any electrical connections to the submersible, which will pull apart and disengage in the event of a basket release.

The jettison requirement also limits the maximum load that can be carried in the basket because of limitations in the release mechanism. This load limit is 400 lbs water weight as measured at the basket release. The scale diagram at left allows investigators and Alvin personnel to calculate basket load using the following formula with two variables: equipment weight and distance from a known point on the submersible:

Σ (Distance (in) x Weight (lbs)) ≤ 20,000 in-lbs

In other words, the sum of all weight/distance products for items to be carried in the basket must be less than 20,000 in-lbs. The limit of 20,000 is derived from the maximum of 400 lbs at the basket release times 50 inches, the distance from the reference point. Using the formula, investigators can design basket loads for a particular dive. The Alvin Expedition Leader has ultimate authority over the final configuration of any basket load.

Special basket configurations and frames for dive-specific equipment or projects can be constructed with advanced notice.

Tape Recorders

Portable audio cassette tape recorders with cassettes are carried
on each dive for scientists’ use. Users are also encouraged
to bring personal tape recorders for replay/debriefing purposes.
Tapes recorded during each dive remain with the user and copies
are not archived. Also, an in-hull open microphone provides
a voice log on the audio track of the primary video tape, which
normally runs for the duration of the “on-bottom”
time.

Video Duplication Station in the Main Lab

Video System

The Alvin video system consists of three principal subsystems:
video sources, recorders, and monitors with source selection
switches. See the Science
Equipment Interfaces section for a detailed description
of the system components.

During the 2001 overhaul period Alvin switched from analog
HI-8mm video tape recording format to the Sony DVCam Professional
format. The tapes used are Sony PDV-124N (124 minute duration).
In order to provide high quality images for both the scientists
and the archives there will be no data routinely burned as overlays
onto the tapes as they are recorded during a dive. Overlay data
will be available on the observer displays during dives and
may be burned onto the original recording if specifically requested.
A time stamp and some dive data will be recorded onto the ancillary
data packet field of the tapes. The time stamp will be visible
on the tape deck display during playback, but the extra data
will not be visible without additional hardware as described
below.

One copy of the original tapes will be made in the Alvin
duplication rack on Atlantis and turned over to the Chief
Scientist. Originals are sent to WHOI as required by the Deep
Submergence Facility Archive Policy.
The copy will be a clone (an exact copy made without decompressing
and recompressing the data and therefore without degradation
of original quality). The clone tapes will be DVCam Pro format
and can be further cloned or copied in the science duplication
rack by the science team (see the PDF document on Video Duplication for additional information below). At the science
duplicating station digital tapes (DVCam or MiniDV from the
sphere camcorder) can be cloned or copied to DVCam/MiniDV tapes
and also copied to VHS, SVHS or DVD-R media. During this process
a pre-defined data set can be burned into the copies as an overlay
if desired. The science program must provide all media associated
with use of this duplicating station.

For DVD copies - one DVD will record two hours of data from tape. Our two-hour DVCam tapes actually contain a little over two hours
(several minutes) of data, so you may run out of DVD space before you get to the end
of the tape.

VHS copies - one VHS tape will record a little over two hours of
information but not exactly the same length as the DVCam tape.

So basically it is a one-to-one duplication process, but not exactly. To copy all the data from tape, you will need to a) do
some editing (to reduce the extra time) or b) have an additional DVD and/or VHS
tape for every dive to make sure you get the extra minutes. Since there are six DVCam tapes produced every
dive, for plan b) you should bring seven DVDs and/or seven VHS tapes for every planned
dive.

Related Files

Viewing Lights

Underwater lights are located outside the viewports. Each observer
viewport has one or more lamps positioned to illuminate viewing
areas. The observer viewport lights are individually controlled
by switches near the viewports and by the pilot’s master
control switches. Additional lighting can be supplied if necessary
but the effect on the power budget must be carefully considered.
Forward illumination is provided by a combination of several
HMI lamps. A 400 watt thallium iodide (TI) arc lamp can be fitted
in place of one of the 400 watt HMI lamps if desired.

Last updated: March 5, 2007

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